Synthesis of the Left-Hand Portion of Geldanamycin Using an Anti Glycolate Aldol Reaction

A synthesis of the left-hand portion of the ansamycin antitumor natural product geldanamycin is reported. An advanced intermediate incorporates the methoxyquinone precursor as a pentasubstituted benzene with a 10-carbon chain that contains 4 of the 6 stereocenters. The key reaction is a novel anti glycolate aldol reaction with a new diaryl-4-oxapyrone used to generate the C-11, C-12 hydroxy, methoxy functionality.